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Nov. 2, 2010 -- Infertility has been ruled out as a potential cause of cerebral palsy among children conceived by in vitro fertilization (IVF) or by intracytoplasmic sperm injection (ICSI), according to a study.

Researchers led by Jin Liang Zhu, PhD, an epidemiologist at the Danish Epidemiology Science Center at the University of Aarhus in Denmark, examined the association between the risk of cerebral palsy in children and the time it takes a couple to conceive.

Although it’s been known that there is an elevated risk of cerebral palsy among children conceived by in vitro fertilization or by intracytoplasmic sperm injection, researchers did not know whether the causes were related to the fertility treatments themselves, the fact that many fertility treatments result in multiple births, or the couple’s underlying infertility that led them to use fertility treatments.

Comparing How Long It Takes to Conceive

Researchers using data from the National Danish Birth Cohort looked at more than 90,000 children born between 1997 and 2003. Participants had been asked whether their pregnancies were planned and how long it had taken them to conceive before a successful pregnancy.

Researchers grouped children by the number of months it took their parents to conceive; parents who conceive quickly are fertile. The groups were zero to two months; three to five months; six to 12 months; and longer than 12 months. Unplanned pregnancies, as well as pregnancies that were the result of IVF, ICSI, and ovulation induction with or without intrauterine insemination were included in the study.

Overall, the time that it took to conceive did not prove to influence the risk of cerebral palsy, even among those who waited 12 months or longer and conceived spontaneously or those who waited the same amount of time and used fertility treatments. The study results showed that:

Among the more than 90,000 children included in the study, only 165 were diagnosed with cerebral palsy.

Among the 3,000 children in this group born as a result of IVF/ICSI, only 17 had cerebral palsy, indicating an estimated risk of the disorder as one in 176.

Among those with cerebral palsy, the percentage was higher among multiple births -- 2.11% among triplets vs. 0.47% among twins and 0.17% among singletons.

Researchers noted the risk of cerebral palsy did appear lower if children conceived through fertility treatments were born as a result of single embryo transfer. The findings were published in the online edition of the journal Human Reproduction, a publication of the European Society for Human Reproduction and Embryology.

“Our research enabled us to examine whether untreated subfertility, measured by time to pregnancy, might be the reason for the higher risk of cerebral palsy after IVF/ICSI,” Zhu says in a news release. “Our results showed that this was not the case because, even for couples who took a year or longer to conceive, there was no statistically significant increased risk if they conceived spontaneously. More research is needed into why there might be an increased risk of cerebral palsy associated with IVF/ICSI, besides the pathway of multiple pregnancies and preterm births. It is also important to remember that IVF/ICSI techniques have developed and improved considerably since 2003, when the youngest children in our study were born.”